Handle bug in bash 4.2 with tilde expansion

Pattern substituion in bash 4.2 was faulty, which caused tilde to not be
expanded in certain cases. This behaviour was previously relied on, now
we are only using that behaviour as a fallback on bash 4.2.

This resolves issue #289
Enable support for Software Collections

Fedora, RHEL, and CentOS provide support for multiple versions of
the same software components using Software Collections.  This
patch lists the active collections in a similar manner to Python
virtualenvs.
From #291: fix $TERM check

Thanks to Daniel Serodio (@dserodio) for the catch.
Simplified unwanted tilde expansion handling

The idea comes from https://github.com/edkolev/promptline.vim/pull/11
Add utility function _lp_bool

_lp_bool converts a return code (default to $?) into a "true"/"false"
value.
Fix #304: _lp_jobcount_color() when is tmux not installed

Refactor _lp_jobcount_color() to avoid running either 'screen' or 'tmux'
if they are not installed.
More _lp_jobcount_color refactoring
Simplify chroot detection code
Synchronize rc, theme, and ps1 files with main file
Fix LP_OLD_PROMPT_COMMAND to work with zsh
Fix *BSD support for terminal colours
Simplifiy git working tree detection

Thanks to @pkkolos (Panayiotis Kkolos <pkkolos@gmail.com>) for the inspiration.
https://github.com/pkkolos/liquidprompt/commit/63e1b8229ba122de3db4c747704d5a13a4b4a109
Count merge commits in git when checking differences with tracking remote branch
Fix mark prefix

Now the prompt mark can be at the beginning
of a new line without a space before it.

Conflicts:
	liquidprompt
Simplify LP_MARK_DEFAULT definition

Thanks for inpiration to @pkkolos.
Fix typos in code comments

Thanks to @pkkolos for catching them in
https://github.com/pkkolos/liquidprompt/commit/1eb35f46b0918974cebe351ca8441e4659b869a5
Fix _lp_bzr_branch_color for zsh

Fixes #301 without affecting bash functionality
Subversion: fix branch/tag extraction

That was broken for a long long long... time.
Should close #117, #237 and is an alternative to patch proposed by
@anthonygelibert in #264.
README: use a true (Unicode) em dash
README: minor fixes