Simplify `expr` targets parsing

Note: '=' (as a replacement to '->') not always works!!

* Remove intermediary `expr\d+` rules
* s/last/expr/g in the `expr` block
* Set `functionCall` precedence to first of `expr`
* Move `lastOnly` to end of `exprMax`
* Rewrite `seqExprs` into `expr+`
* s/exprM/exprMax/g
* s/exprA/expr/g
* s/exprAs/exprs/
* Use `exprMax` instead of custom rule `vap`
* Fix (reversed) precedence in `expr` & `matchable`
* Update/Add tests in consequence
* Fix precedence in `map` contents

Other fixes

* Remove `map` & `record` useless & harmful >-separator
* Fix wrong `catchClause` code & test 7
* Fix testsuite PNG names misalign of 44.png
* Move `atom` into its right place: inside `term`
* Fix some comments
* Remove -Xmx8g Java option that allocs more VMEM
* Code style: leaner writing of plural-rules
* Revert special lexing case ‘for PHP programmers’
    : no incentive to use such “reserved” atoms
* Forbid lexing - in atoms
    (- would replace _. It also allows Erlang's syntax for binaries)
* Replace `if` by `cond`
* Add a one-line `if`. else = `if not`
    : no new keyword here
Merge pull request #31 from fenollp/refactor-expr

Simplify `expr` targets parsing