Rudimentary table support

[seato]

This PR adds an imperfect workaround for adding table support by adding two spans: ClickableTableSpan and DrawTableLinkSpan.

These spans provide limited table support by reconstructing the HTML and passing it to an app-defined implementation of ClickTableSpan (which could possibly forward it to a WebView similar to what's shown in the example).

The DrawTableSpan does not need to be implemented, but we expose it so that applications can display text other than "[tap for table]", which is useful for localization.

This PR is imperfect because once we start keeping track of a table tag, we are only able to keep track of other tags which android doesn't handle by default, so the raw html passed to the ClickableTableSpan won't necessarily be correct.

[seato]

If this looks good to merge, then I'll add a commit to update the README to reflect table support.

[seato]

Also if it looks good, I'll add the proper Apache headers. I just realized I left them off.

[dschuermann]

Yes looks okay, I think that the usefulness is limited but I am willing to merge :)

Please add the license headers and README additions as you proposed.

[seato]

@dschuermann Applied the changes we discussed; I also increased the version in the build and README to 1.4 but I didn't update the tag because I see it's at v1.4 so I'm not sure what kind of system we've got going on there.

[seato]

@dschuermann What should happen if the HtmlTextView encounters a table but the developer doesn't implement a ClickableTableSpan?

ATM I provide a default implementation for DrawTableLinkSpan which means <table>...</table> gets replaced with [tap for table] (unless the dev provides their own implementation), but tapping the text does nothing.

There's two routes we could go about this:

1. Provide a default implementation for ClickableTableSpan which crashes if the HtmlTextView comes across a table and the user/dev clicks the replacement text.
2. Crash in HtmltextView.setHtmlFromString() which is pretty early so that it developers don't miss it.

I like the idea of crashing early so that devs don't get caught with their pants down, but I can also do what you do with image getters and just log an error. Thoughts?

[dschuermann]

I think currently, every tag that is not supported is simply not displayed. I would propose we do the same for tables if no ClickableTableSpan has been given and simply omit the whole table, even not showing [tap for table].

[seato]

@dschuermann Updated the PR and the default behavior is to not render the tables.

[dschuermann]

thanks!

[dschuermann]

and released to jcenter...