Add Unified Expression Language (EL) and include it in JSP

[MoritzKn]

This is my attempt to implement #64.
Because other technologies (like JSF) use EL as well, the EL grammar is added as its own language file.

There are a few things I am unsure about:

• Is source.java.el a good scopeName?
  The problem I see is that snippets, autocomplete providers and alike which are intended to work with Java will also apply to EL.
• Should I add test and if so, how?

Some JSP code I used for testing:

${foo}
${fooBar}
${42}
${foo42}
${42foo}
${fooeq}
${foodiv}
${foomod}
${notfoo}
${footrue}
${42+4}
${42==4}
${'bar \' \\ sdaff " dsaf'}
${"dsa f ' 'dsaf sdf \\ \" asd fds af"}
${"foo"eq"foo"}
${foo eq bar}
${foo == bar}
${foo==bar}
${foo ne bar}
${foo !=bar}
${0 lt 5}
${0 < 5}
${8 gt 5}
${8 > 5}
${80 le 5}
${80 <= 5}
${42 ge 0}
${42 >= 0}
${42 + 0}
${42 - 0}
${42 * 0}
${42 div 0}
${42 / 0}
${42 mod 0}
${42 % 0}
${not bar}
${!bar}
${"foo" eq 'foo'}
${"\"'" eq '"\''}
${true}
${false}
${fn:contains('foo', 'bar')}
${foo ? 'foo' : 'bar'}
${foo['bar']}
${foo[42]}
${(42 lt 5) and (45 ne 8)}
${fn:indexOf('fooo', 'o')}
${not empty bar and fn:contains(bar, 'foo')}

<c:if test="${not empty bar and fn:contains(bar, 'foo')}">
    ${bar}
    ${setFoo(true)}
</c:if>

[MoritzKn]

Here are a few EL examples from the oracle page: http://docs.oracle.com/javaee/6/tutorial/doc/bnaim.html#bnain

[winstliu]

Is this a grammar that someone will ever want to explicitly choose in the Grammar Selector? If not, this line should be removed.

[winstliu]

🔥

[winstliu]

Why not just include all the patterns here directly?

[MoritzKn]

The primary new feature of JSP 2.1 is the unified expression language (unified EL), which represents a union of the expression language offered by JSP 2.0 and the expression language created for JavaServer Faces technology

-- https://docs.oracle.com/javaee/5/tutorial/doc/bnahq.html

Meaning the unified el grammar could also be useful outside of JSP in a JavaServer Faces (JSF) context. Therefore I thought a separate grammar would make sense although no JSF language package exists yet.

[winstliu]

So does #el only contain the expression language up to JSP 2.0? And that perhaps in the future someone may add support for JSP 2.1 in this file?

[MoritzKn]

Ups, I mistaken the code snippet for something else and comply misunderstood you. 🙈
Ignore my first comment. You are right, it makes no sense to include everything like this. I probably just copied this from some other grammar without understanding what exactly it meant.

[winstliu]

Also yes, specs will be required for this PR. I think some basic tests for each pattern should suffice.

[MoritzKn]

@50Wliu rebases against master, fixed your remarks and added specs.