Avoid unnecessary EL parsing

[ggeorgovassilis]

Text (e.g. <node>text</node>) and attribute values (e..g <a attribute="value">) are evaluated by EL with every rendering invocation; it is probably faster to determine during parsing which values contain EL and submit only those for evaluation.

[ggeorgovassilis]

This ticket should be substantiated with profiling information

[ggeorgovassilis]

idea: add a boolean variable (or maybe subclass?) that is initialised during node creation to "true" if text contains an EL expression; rendering could then simply check that variable. As always: profile the alternatives to prove that they are useful.