Implemented History copying to the clipboard
Make the default history item length to be the same as the limit for the headwords.

So, it is 256 now.

And configurable via the same parameter in the config file: maxHeadwordSize.
Preserve the current index in History list when a single entry is deleted.
Lupdate all translations, update Russian translation
Compare History items case insensitively.
Remove rather useless context menu to add title to history.

In most cases, since we are on this page, we have already
just added its title to the history.
Revert "Remove rather useless context menu to add title to history."

This reverts commit c03b3461140df2b24e01e9203325b723cbe0fd6f.

The menu item is not completely useless, it useful when the automatic history
gathering is disabled and this menu could be used to add items to the history
manually.
Better way of dealing with adding title to history.

We only show that menu item to add the title to history if the
history is set to only collect the entries manually.