Review all commandline flags

[trufae]

some letters are a bit confusing, let's rethink them

Usage: fsmon [-jc] [-a sec] [-b dir] [-B name] [-p pid] [-P proc] [path]
 -a [sec]  stop monitoring after N seconds (alarm)
 -b [dir]  backup files to DIR folder (EXPERIMENTAL)
 -B [name] specify an alternative backend
 -c        follow children of -p PID
 -f        show only filename (no path)
 -h        show this help
 -j        output in JSON format
 -L        list all filemonitor backends
 -p [pid]  only show events from this pid
 -P [proc] events only from process name
 -v        show version
 [path]    only get events from this path

[trufae]

my proposal:

• -a should be -t for timeout instead of alarm.
• -B should be -b or maybe find another flag like -a
• I would probably change -b or exchange with -B

The other flags lgtm, unless we want to change a flag for a -m mode (mode=json,stream,tsv, ..)