[compiler] Allow parse_logic_expression to return the parsed expression
[compiler] Add a method is_valid for recipe_expression

The code moves from recipe.cc to recipe_expression.cc for consistency,
but no real new code.
[compiler] Add the relation binary_kind -> string in the interface

No functional changes
[compiler] Add a recipe_expression ctor with only one recipe_decl
[model] Make ability_test able to really send some constraint

It now uses the same syntax than in recipe description. Probably still a
lot of bugs to discover
[doc] Complete the first agent tutorial, using the new test features
[doc] Complete the second tutorial

Fix some issues after testing
Add some examples of control of the agent.
[compiler] Honor verbose switch

Add a verbose boolean state in universe, and only print 'information' if
it is turned on. The default behaviour is 'quiet'.
At hyperc level, pass the right value to universe, depending of the
command line switch
[model] Be quiet if not at least in debug mode.

While here, fix a typo
[model] Don't need to start ability_test in DEBUG_ALL mode

INFORMATION is largely enough
[model] Add a random part in name of ability_test

It permits to start multiple instance of it in the same time, for
example, one to set a constraint, and a few ones to get the values of
several variables.
[compiler] Get INCLUDE_PATH from environment too
[doc] Sync man with the reality

- Mention environment variable
- verbose option does not support anymore argument