Accept both loose and strict parsing of versionnumber

[o314]

It could be useful to accept parsing of versionnumber eitheir more strictly, or more loosely ;
instead of only parsing more loosely as for now.

I have just spent hours debugging a mismatch between conda and julia around version
that could have been fixed very earlier if strict mode was reinforceable

Here are some regexes that could help for that

ver_strict_re = 
    r"""^
    (?<major>\d+).(?<minor>\d+).(?<patch>\d+)                   # core
    (-(?<pre_rel>[\d\w-]+(.[\d\w-]+)*))?                        # pre_rel::qid
    (\+(?<build>[\d\w-]+(.[\d\w-]+)*))?                         # build::qid
    $
    """x

ver_semistrict_re = 
    r"""^
    (?<major>\d+)(.(?<minor>\d+)(.(?<patch>\d+))?)?             # core
    (-(?<pre_rel>[\d\w-]+(.[\d\w-]+)*))?                        # pre_rel::qid
    (\+(?<build>[\d\w-]+(.[\d\w-]+)*))?                         # build::qid
    $
    """x

built around the inlining of

qid = r"[\d\w-]+(.[\d\w-]+)*"
id = r"[\d\w-]+" # approx

Please note that the id, qid are only an approximation of semver ones today

[stevengj]

If you want strict mode you can just do VersionNumber(string), no? The whole point of vparse is to supplement this with something looser.