Create new parser version 4

[KungFuFurby]

Citing https://smwc.me/1599381 and the few replies I have received, I will go through with parser version 4.

Parser version 4 will do the following:

• Incorporate what was implemented in Adding dotted notes, = lengths and tie support to l directives #1

All older versions will output warnings for running into the following...

• Using uppercase letters as note data (Undefined reads occurring when reading pitch with uppercase letters #246)
• Using o while specifying a note on a $DD hex command (Song compiler freezes during hex validation when an octave is specified on $DD command #27)
• Using fractional note lengths (#halvetempo and #option dividetempo are not actually dividing lengths by the tempo ratio #304, whose fix debuts for parser version 4 first)

I will also support some of the parser version 3 features as indicated in #216. Anything related to new hex commands will not be covered, and conversions in particular are parser version 3 only.
The following also needs to be done...

• v, t and w need to have their durations divided by the tempo ratio. I cannot correct this for parser version 3 because it was like that as of the last public release in May 2017, but I can do this for parser version 4. I later discovered that this would not have worked because of #halvetempo and #option dividetempo are not actually dividing lengths by the tempo ratio #304, therefore I had to implement a fix through that.

[KungFuFurby]

Although #allsamplesimportant and #notranspose could have been implemented from parser version 3 for this parser version, I have instead merged the pull request and closed the issue for the time being.