Definition expansion for "pattern"-type definitions

[clange]

Besides simple "symbol := expression" definitions (#110), pattern-based definitions like "f(x) := expression(x)" are eligible for expansion:

<definition for="symbol-URI" type="pattern">
  <requation>
    <OMOBJ><!-- f(x) --></OMOBJ>
    <OMOBJ><!-- expression(x) --></OMOBJ>
  </requation>
  <!-- potentially more such equations, but for now we ignore that -->
</definition>

@Michael: What kind of pattern matching (or unification?) would be needed for handling this correctly? – I have no idea and think we should start by only supporting cases as simple as f(x) or f(x1,...,xn).

[clange]

Do this before MKM if it's easy to implement.

• if we use FlOMDoc: @Florian: Does FlOMDoc already support such definitions?
• if we still use JOMDoc: do not waste time on implementing it within the servlet, instead postpone the ticket past MKM

[clange]

This may be a task for the guided research, or for some later work on JOBAD in any case. Therefore we can not yet give a reliable deadline.