Detect unstaged changes

Abort when there are unstaged changes in the repository being processed.
Improve handling of unstaged changes

Script now asks user if changes should be discarded (git co -- .)
instead of simply aborting in error.
Delete 'admin' dir at end of process

Asks the user if they want to delete the 'admin' directory, and if not
displays a warning to remind them to do it manually afterwards.
update-tracker.sh: handling of 'admin' directory

The new process now check if there are untracked files in the repo. If
yes, ask user if changes should be discarded, and abort if not.

Then at end of script, the user is asked if 'admin' dir should be
deleted.

This is easier to implement than a new commit in the local branch to
remove the directory, because this way we don't have to deal with
potential merge conflicts which would be difficult to handle in an
automated way.

Fixes #16345
buildrelease.py: remove extra space in digest file name
Fix error with --clean and relative paths
Move GPG signing to function
Move checksums generation to function
Move build dir removal to function
Force generation of GPG signature file
PEP8 coding guidelines, whitespace
buildrelease.py: enhancements and bug fixes
More issues with relative paths

Fixes problem of release files not available in the target directory at
the end of the process when doing a fresh clone in an unspecified
directory (ie. when the script creates a temporary clone).
Use check_call() instead of call() for rsync

Throws an exception in case the copy fails
Allow use of externally defined reference file

If REF_FILE variable is set, that file will be used as reference to
determine the old copyright year. If not, core.php will be used.
More descriptive filename for db cleanup script
Use a single update statement instead of 4
Define the realname
New script to dump and anonymize Mantis DB

Script will create a clone of the specified mantis database, run
db-anonymize.sql script to cleanup the data, then dump the clone in
compressed format in the target directory.
Database dump script