#593 Allow annotations on algebraic variables

• Best to review per commit.
• Some additional changes for the CIF code generator:
  • C89/C99/Simulink code generation: algebraic variable JavaDocs now end with ., not ;.
  • C89/C99/Simulink code generation: algebraic variable JavaDocs had a newline too many.
  • C89/C99 code generation: algebraic variable JavaDocs are now on a single line if the algebraic variable has no documentation annotations.

Addresses #593