Feat: Analyze logsources

[andurin]

This PR brings a new sub-command to sigma analyze which prints a simple table about the used logsources.

Example:

$ sigma analyze logsource - ../sigma/rules/windows
Parsing Sigma rules  [####################################]  100%          
--------------------------+---------+----------+------+--------+-----+---------------+-----
Logsource                 | Overall | Critical | High | Medium | Low | Informational | None
--------------------------+---------+----------+------+--------+-----+---------------+-----
process_creation          | 1082    | 25       | 519  | 486    | 51  | 1             | 0   
None                      | 320     | 13       | 161  | 105    | 35  | 6             | 0   
registry_set              | 182     | 0        | 97   | 77     | 7   | 1             | 0   
ps_script                 | 160     | 2        | 51   | 88     | 19  | 0             | 0   
file_event                | 151     | 7        | 79   | 58     | 7   | 0             | 0   
image_load                | 90      | 1        | 41   | 44     | 3   | 1             | 0   
network_connection        | 49      | 0        | 24   | 23     | 2   | 0             | 0   
registry_event            | 35      | 9        | 18   | 8      | 0   | 0             | 0   
ps_module                 | 33      | 1        | 17   | 10     | 4   | 1             | 0   
process_access            | 23      | 1        | 17   | 4      | 1   | 0             | 0   
pipe_created              | 17      | 6        | 3    | 7      | 0   | 1             | 0   
dns_query                 | 17      | 1        | 3    | 10     | 3   | 0             | 0   
file_delete               | 12      | 0        | 4    | 7      | 1   | 0             | 0   
create_remote_thread      | 11      | 0        | 8    | 3      | 0   | 0             | 0   
ps_classic_start          | 10      | 0        | 2    | 5      | 3   | 0             | 0   
driver_load               | 10      | 0        | 7    | 2      | 1   | 0             | 0   
registry_add              | 9       | 0        | 4    | 4      | 1   | 0             | 0   
create_stream_hash        | 9       | 0        | 6    | 3      | 0   | 0             | 0   
registry_delete           | 7       | 0        | 3    | 4      | 0   | 0             | 0   
file_access               | 7       | 0        | 0    | 5      | 2   | 0             | 0   
wmi_event                 | 3       | 0        | 2    | 1      | 0   | 0             | 0   
file_change               | 2       | 0        | 2    | 0      | 0   | 0             | 0   
raw_access_thread         | 1       | 0        | 0    | 0      | 1   | 0             | 0   
process_tampering         | 1       | 0        | 0    | 1      | 0   | 0             | 0   
sysmon_status             | 1       | 0        | 1    | 0      | 0   | 0             | 0   
sysmon_error              | 1       | 0        | 1    | 0      | 0   | 0             | 0   
ps_classic_provider_start | 1       | 0        | 1    | 0      | 0   | 0             | 0   
file_executable_detected  | 1       | 0        | 0    | 1      | 0   | 0             | 0   
file_rename               | 1       | 0        | 0    | 1      | 0   | 0             | 0   

Edit:
Columns are sortable using -k/--sort-by switch:

$ sigma analyze logsource --sort-by Critical - ../sigma/rules/windows
Parsing Sigma rules  [####################################]  100%          
--------------------------+---------+----------+------+--------+-----+---------------+-----
Logsource                 | Overall | Critical | High | Medium | Low | Informational | None
--------------------------+---------+----------+------+--------+-----+---------------+-----
process_creation          | 1082    | 25       | 519  | 486    | 51  | 1             | 0   
None                      | 320     | 13       | 161  | 105    | 35  | 6             | 0   
registry_event            | 35      | 9        | 18   | 8      | 0   | 0             | 0   
file_event                | 151     | 7        | 79   | 58     | 7   | 0             | 0   
...