Upgrade macros to new specs and add theme support

[ebbypeter]

This is an upgrade long overdue. Archimate have deprecated define and definelong parameters replacing it with function and procedure. This PR is to upgrade the macros to use the new recommendations. Additionally, theme and nesting support is added to the library. This should take care of the following issues #41, #42, #43

Changes:

• Updated macros to use 'procedures' as per current PlantUML recommendations.

New Features

• Theme support.
• Nesting capability for most components
• New Theme: Standard
• New Theme: Alternate
• New Theme: Saturated
• New Theme: Low Saturation
• New Theme: Handwriting

[ebbypeter]

@Potherca Do you have time to review this PR?

[Potherca]

Great work @ebbypeter! I hope you don't mind the slow response, you caught in the middle of wrapping up a project and taking a vacation.

I reviewed the change post-merge, looks good to me. Love the themes as well!

Other than some personal-preference style things, the only feedback I have is:

• In the README, do we also want to mention that things can be loaded using !include <archimate/Archimate>?^1
• Most of the samples have a title after the @startuml, but samples/Archimate-Relationships.wsd and samples/Archimate-Sample01.wsd are missing one?