fixes #15 SKIP_EMPTY_LINES feature for csv parser

[vboulaye]

I started an implementation of the SKIP_EMPTY_LINES feature based on the existing ALLOW_COMMENTS.
When enabled It ignores both empty and blank lines.

Do you prefer to have SKIP_EMPTY_LINES and a new SKIP_BLANK_LINES as separate features? or is it good enough to adapt the description of SKIP_EMPTY_LINES?

[cowtowncoder]

I don't think 2 features are needed, but I think SKIP_BLANK_LINES might be better name -- this because there are a few priori cases like String.isEmpty() that specifically do not check for "all whitespace" case.

[vboulaye]

I renamed the feature to SKIP_BLANK_LINES (and all the references in the code).

Is there something to do to handle the deprecation since the old name SKIP_EMPTY_LINES has already been published?

I also made a change to the CommentsTest to include a test case where the '#' character is preceded only by whitespaces. This is a case that is described in CsvSchema.setAllowComments but was not explicitly tested.

Regarding the documentation, I did not modify the javadoc html as I assumed it is generated, but I could not find from where.

[cowtowncoder]

Oh shoot. I did not remember that SKIP_EMPTY_LINES did exist. I thought that was being added.

Now: since support had not been implemented, I'd have been ok to change it for 2.10.0, but since that ship has sailed, I think we have 2 choices:

1. Use SKIP_EMPTY_LINES, implement for 2.10.1 (no api change, just fix to make existing feature work
2. Replace SKIP_EMPTY_LINES with SKIP_BLANK_LINES for 2.11(.0), as API change, deprecating old feature.

To me (1) seems like a better choice actually; we do need to document it, but that's fine.
Then we could do renaming for 3.0.

Apologies for not checking this before asking you to change this.

[cowtowncoder]

Need to add @since, once we figure which branch this should go in. Same for new methods.

[vboulaye]

I added @since 2.10 to the feature + the new method that replace the skip comments.
I am not sure where else I should put it.

[cowtowncoder]

I usually add to method and field, but not a big deal for internal fields.

[vboulaye]

I reverted the name of the Feature to SKIP_EMPTY_LINES and added ̀@SInCE 2.10` as it was added in 2.10 anyway

[cowtowncoder]

Ugh. There's a pretty nasty bug in here. Code fails to take into account the fact that only part of the document may be in buffer, leading to #191 ... :-( :-( :-(.