Rename "Document" menu to "Documents"

A "Document" window suggests finding commands related to the current document while this menu actually is a list of all open documents
ly/util.py: Add range check for int2roman

roman numerals must be positive integers, but the current implementation
of int2roman processed negative numbers without complaining.

Now the function immediately raises a ValueError if input < 1.
allow outline regexp to have "title" group, which is displayed if existing, instead of the whole match
Merge pull request #133 from uliska/ul-UI

Rename "Document" menu to "Documents"
Merge pull request #139 from uliska/int2roman

ly/util.py: Add range check for int2roman
pot update, nl.po
some updates to the word list
findOpenView by default; and it even could be made configurable later
cs po update
outline: allow "text" as a group name and make items bold if "title" is used
document the outline view comfiguring a bit more; there is however a little bug: you cannot use the "title" or "text" named group in more than one expression, as those are joined and Python does not allow the same group name more than once.
document it, even though the multiple named group issue needs to be resolved
pot/nl.po upd
seealso not needed
outline: now you can the same named group in multiple regexps; they are suffixed with a number on generation
outline: new "alert" named group with an italic, reddish style
always draw splash
nl po typo
correct encoding in pt_BR
man page by Ryan Kavanagh, thanks!