Fix to prevent illegal cast

Now ccprover ignores theorems using lamda expressions.
Also removed redundant case in buildPExp
Merge pull request #126 from mikekab/master

Fix to prevent illegal cast
converted all vcs to the immutable form expected by the in house provers
invoking the in house provers work as intended.
new output class for VCs
output to file complete
Merge pull request #127 from yushan87/vcgen-output

VCGenerator Updates (July, 2014)
stores each RESOLVE Conceptual Element as we visit them
function assignment rule
corrected and completed function assignment rule
don't need parameter ensures as givens
no need to modify the ensures clause when we encounter an evaluates mode parameter
changed the output string from ? to '
getting rid of the section id counter in the vcgenerator.
don't really need to keep track of what we visit in a stack (could use the stack visitor if we wanted to keep track...)
renamed a variable
reformatted files
added a stack for assertive codes that we haven't processed yet
skeleton for the if/else rule
complete if/else rule