allows to style buttons as though internal links

by assigning class="tc-btn-invisible tc-tiddlylink"
fixes #1010

safe / sequential replacing of formatstrings for date conversions

please review & test
fr-FR translation for three introductory tiddlers on Filters.
add Japanese Translations
documentation for making buttons look like links

added instructions to button widget documentation
Merge pull request #1229 from tobibeer/fix-1010

fixes #1010 sequential date formatstrings
Some tests and style updates for #1229

@tobibeer I simplified the handling of matched strings a little.
Update cla-individual.md
Add heeg.ru to resources
Merge pull request #1230 from pekopeko1/japanese5.1.6

add Japanese Translations
Merge pull request #1233 from xcazin/fred2

fr-FR translation of three introductory tiddlers on Filters
Merge pull request #1236 from anavarre/master

Add Aurelien Navarre to cla-individual.md
Filename will now be set to "tiddlywiki.html" when path does not contain a filename.
Update Using Stylesheets.tid

added documentation for html in StyleSheets

https://groups.google.com/d/msg/tiddlywiki/Qx0y7btud5M/Ch6hMnh0ud0J

simplified the specificity section, some rewording
Remove unused local variables
Merge pull request #1238 from Drakor/fixDownloadSavingHandler

Filename will now be set to "tiddlywiki.html" when path does not contain...
updated documentation for link-button
Merge pull request #1228 from tobibeer/button.tc-tiddlylink

allows to style buttons as though internal links
Updated Dutch translation

Thanks @gernert

I’ve not updated GettingStarted because I plan to do one final
redrafting before 5.1.6.

I’ll put up a prerelease for you to play with in a couple of hours when
I get to better wifi!
Proposing to change to a more appropriate tag / category

From "Feature" To "Customise TiddlyWiki"