Initial logic to remove SQL-style comments.

In SQL, comments can be noted in two different ways. This logic
removes the type I use the most which is two dashes "--". Much like a
"#" in R, the double dashes can appear anywhere in a line. From that
point on, the line is considered to be a comment.

Also adds a simple gsub to remove the resulting double spaces in the
returned query which makes it easier for users to read the query.
Merge branch 'dev' of github.com:Choens/sqlutils
Separates functions more cleanly into individual files.

Just makes it easier to find things.

Modified   R/cacheQuery.r
Modified   R/getSQL.r
Modified   R/sqlPaths.r
Modified   R/sqlexec.R
New		   R/execQuery.r
New		   R/getCacheFilename.r
New		   R/getSQLRaw.r
New		   R/recodeColumns.r
New		   R/sqlFile.r

This does not affect the stuff from roxygen2. I'm leaving that alone
for the time being.
sqldoc() now handles the SQL version of Roxygen comments.

SQL Roxygen comments are now "--'" which is directly inspired by
Roxygen comments which are "#'".

This needs more testing, but it appears to handle the following query
correctly:

--' This query pulls some_col from table foo.
--' This query is effectively a bullshit test of sqldoc().
--' @param bar This is my example parameter.
select some_col
-- I should not be returned by sqldoc().
from foo
where :bar: = 6 -- end-of-line comment. I should not be returned by sqldoc().
;

When this query is parsed by this version of sqldoc, the first three
comment lines ARE returned. The last two are not, which is exactly
what we want.
Merge pull request #5 from Choens/master

SQL Comments in sqlutils.