UserSpace: clean 3pi.-00 and pi_2eta.-00 directories

Remove the prefixes '3pin' and 'pi-2eta' from the filenames, this is
already included in the directory name. Adjust the path to the particle
data table in GenerateKeyfiles.sh, compared to the old 'keyfiles'
directory, there is one more intermediate directory. Added an example
generator configuration file also for pi-etaeta.

(cherry picked from commit 3a2945b6b4ae680a81d2cdf7e24253d3816628df)
UserSpace: modernize 3pi.--+ directory

Modernize the directory for the pi- pi- pi+ channel. Updated the example
generator configuration to work with the current generator, also updated
the target description to a hydrogen target. Removed the existing
keyfiles and wavelist, updated the template for the wave set generator
and added a number of wavelist of previous experiments. Also added a
script calling the wave set generator and taking care of creating the
special mass dependencies.

Basically this is a copy of the directory for pi- pi0 pi0 with changed
pion charges.

(cherry picked from commit 9450af8ef8bda6d3aaa3fe70c3b71051ede34d92)
buildSystem: Fix bug in git hash getting.

Apparently, with some git installations, there was a problem when getting the
latest git hash when environment.cmake was run, because git did not recognize
the full path to the repository as belonging to the repository (*sigh*). Fix
this by running git within the repository and not specifying any path.

(cherry picked from commit b41807515af49d867971369d8ee87532c9f65638)
Remove unused include file

Remove 'TRegexp.h' include, only 'TPRegexp' is used.

(cherry picked from commit 696eef426a3aaf02a1c9e45d60a5ed724e3aec2b)
Use PCRE for matching patterns to wave/amplitude names

Use PERL compatible regular expressions to match wave or production
amplitude names to patterns when getting the corresponding indices to
e.g. calculate total intensities/intensities for more than one wave.
The usage of 'TRegexp' is replaced by 'TPRegexp'. Obviously PCRE are
much more powerful than the version of regular expression used before,
patterns compatible with the old version should work just as before.

(cherry picked from commit bd5f238870ab7ea77ccd9ed2cbe9bd2a9b93c329)