new parser for lp files

[fblanqui]

This PR provides a new parser for lp files not based on Menhir but written by hand. It provides better error messages and is easier to change later if needed. It also integrates search queries properly. Performance is equivalent, even slightly better.

Other changes:

• rename rw_patt into rwpatt
• reorganize pos.ml
• fix p_[term|rw_patt]_of_string not called with correct position #1325
• rename type inside into relation, and constructor QOpp into QOp

TODO:

• fix parser.ml to parse strings and other entries with the new parser
• extend the parser to the search command and patterns
• fix problem with tests/OK/Tactic.lp
• fix initial position when parsing a search query/term/etc. from a string
• remove searchQuerySyntax.ml and lpParser.mly
• rename the new parser file to lpParser.ml
• fix extend_pos (use beginning of 2nd position)
• an application cannot start with a square bracket [t]
• do not allow applications of the form h \x,t
• remove dot in rewrite patterns
• accept "id+ : term" for parameters ?
• improve extend_pos further by recording the end of the previous token?
• in case of unclosed parenthesis/bracket, give the position of the opened parenthesis/bracket
• replace command and modifier tokens by specific UID's ?