Trim whitespace from event source identifiers. Fixes #701

[jconnop]

Link to issue(s) this covers

Problem

#701

Solution

• When 'Handles' identifier is on new line, it gets prefixed with a bunch of whitespace. i.e.

                                          Button2

• So after getting this identifier from syntax tree / library calls, trim it before escaping and using.
• At least one test covering the code changed

[GrahamTheCoder]

Wow. I've seen some weird stuff from VB before. But parsing whitespace on the identifier sounds like a pretty serious library bug. Thanks for the workaround. I'll try to have a proper look soon and see if this needs raising in dotnet roslyn repo