Add snippets for VHDL & OSVVM

[fsasm]

Add some useful snippets for OSVVM. For example, the library and context clauses for OSVVM, or template for testharness, testctrl and the configuration.

• procedure and function
• library and context clause for OSVVM
• process with reset without else-branch
• entity instantiation
• full vhdl template with library clause, entity declaration and architecture
• signal and variable declaration
• small things like when clause
• whenc for when inside case
• entity declaration with generics