Add the alternative grammar, modify the standard grammar

Add the new alternative grammar, which is C#-like and human-readable.
Modify the standard grammar, make optimized and clean.
Modify the Grammar class to report duplicated key name.
Rename category names

Rename the root grammar category name ('yacq' and 'alt.yacq') to unified new
name 'root'.
Implement primary expressions in the alternative grammar

Implement primary expression rules (parentheses, member accesses, invocations)
in the alternative grammar.
Correct copyright lines in grammar classes
Implement transiting expressions, add a punctuation character

Implement transiting expressions to place an expression with the alternative
grammar in the standard grammar context, and vice versa.
Make '#' a punctuation (reserved) character in both the standard and
alternative grammar.
Fix the primary expression rule in the alternative grammar, allow whitespaces.
Add vector expressions and fix colon infixes in the alternative grammar

Add vector expression rule in the alternative grammar.
Fix a bug of the colon infix rule in the alternative grammar.
Add YacqServices.DefaultReader property

Add DefaultReader static property in YacqServices class to be able to select
default reader (and grammar).
Fix bugs in assignment operators

Fix the behavior bugs about associativity of assignment operators (the root
function symbol and the operator in the alternative grammar).
Merge branch 'feature/alternative-grammar' into develop