How to interface tlmgr search with keywords

new search interface:

tlmgr search <options> <literal>
	searches the normal way, i.e., pkg names, short/long desc
tlmgr search <options> --file <literal>
	searches the current --file way, i.e., the list of files of a package
tlmgr search <options> --taxonomy <literal>
	searches the taxonomy (keyword, functionality, characterization)
tlmgr search <options> --extended <terms>
	allows full searching (will maybe implemented later)

<options> ::= --global | --word | --list [keywords|functions|characterizations]

<terms> ::=  <term> | <term> <terms>
<term>  ::=  AND  | OR  |  LEFT | RIGHT
              keyword=<literal> | function=<levels> | 
	      characterization=<levels> |
	      package-name=<literal> | title=<literal> |
	      description=<literal> | file=<literal>

<levels> ::= <level> | <level> " > " <levels>
<level>  ::= <literal>


defaults = package-names=ARG OR titles=ARG OR descriptions=ARG
AND -> conjunction
OR  -> disjunction
LEFT|RIGHT -> parenthesis for grouping of and and or

<literal> may contain wildcards and it is matched in a glob style (no re!!)


example
	tlmgr search keyword=paragraph AND description=dropped
should give back the lettrine package

	tlmgr search characterization=bibliography
searches for all packages with characterization containing anywhere the string
"bibliography" (case insensitive).

