Improve performance of Location constructor, by avoiding exception throwing when path is not an URL
Move Bio-Formats downloads page under the main repository

- Convert Bio-Formats downloads page into Sphinx format. Page can be generated
as usual with `make html` and sphinx_theme can be applied as for the regular
Bio-Formats documentation.
- Add release download page build as part of the Travis build
Fix indents in index.html
Remove develop-specific artifacts
Re-expose the OME editor artifacts in the component table
ND2Handler: parse numbers defensively

Several numerical parsing methods throw NumberFormatException when
the input string is not actually a number. In particular:

* Integer.parseInt(String)
* Double.parseDouble(String)
* new Integer(String)
* new Double(String)

The ND2 handler parses a large number of string key/value pairs,
converting values into numbers in many cases. But in almost every case,
no error handling was done in case the input value was not a number.

This change adds a blanket try/catch for NumberFormatException around
areas that parse lots of numbers, emitting a warning for any
non-conforming key/value pairs. This allows parsing to continue,
hopefully resulting in a less fragile ND2 reader.

It also catches NumberFormatException separately within the nested
TextInfoItem parse loop, so that parsing of TextInfoItem entries fail
individually rather than all-or-nothing.

Note that this change is nearly all whitespace indentation; the easiest
way to view the "real" change is using "git show -b" on the commit.
Merge pull request #691 from ctrueden/nd2-defensive-parsing

ND2 defensive parsing
Merge pull request #690 from sbesson/rebased/dev_4_4/downloads_page

Bio-Formats downloads page (rebased onto dev_4_4)
Merge pull request #683 from kuba97531/dev_4_4

Avoid throwing exception when parsing URL in Location constructor