More explicit output error message when git not found
Add helpers methods

- git-describe is not going to fit anymore since pre-release metadata could
contain hyphens as well
- add helper to count the number of commits from the most recent and
reachable tag
- deduce maj, min and patch from the last tag rather than from git-describe
Add version formatting helper, custom formatting, remove "update-promote"
Update commands' help
Update gitver's versioning template
Update configuration parser, write commented default configuration file
Merge branch 'semver'
Always show NEXT and pre-release metadata, mark used data with "Using"
Fix casing, unneeded string concatenation, add parenthesis on unused data
Add "current" command, output current version only, without any formatting
Fix missing color output on error
Add missing template check, a valid output shall be defined at line #0
Update documentation with new 0.3.x functionalities