MidiFile load and cleanup Midi docs

[ghost]

Implemented Error MidiFile.load(file_path) that can load a midi or soundfont file from anywhere on the filesystem.

var mf = MidiFile.new()
mf.load("/users/myuser/Desktop/sounds.sf2") #works from anywhere

Cleaned up midi docs:

• changed all code examples to use the importer instead and references new MidiFormat FORMAT_SF2 and FORMAT_MIDI instead
• fixed inconsistencies in language, spelling, grammar and punctuation and incorrect explanations
• explanations are even more detailed
• parameters from description have dual naming where appropriate that overlaps with InputEventMIDI such as volume/velocity or note/message. Note: built in InputEventMIDI uses very technical language that is confusing for example note is message which is technically correct as notes are ON OFF messages but confusing or volume is velocity which is also technically correct and also confusing.

[ghost]

I'm develping on Windows and msvc is really forgiving compiles on anything hahaha. I never catch some of these gcc or non windows errors in time.

[Xrayez]

There are other stuff that could be fixed but ok to merge... Thanks!