Fix too-long lines around user avatar "button"

The user avatar "button" in the header had lines that were slightly
too long to its left and right. I finally tracked this error down to
its source. Using "position: relative" was correcting the positioning
of the element, but leaving a space for it in the "original" location,
which was in turn causing its containing div to be a bit too large.
Add button navbar for routing/views

Two of these buttons should become drop-down menus; this has yet
to be implemented.
Submenus for buttons that need them

Still need to tweak submenu CSS a bit to make it look better, but
this is a good start. Also need to implement some Angular animation
to make it all look good: the chevron should flip, the submenu should
fade (or slide) into view and away, and the menu should go away once
it hasn't been hovered on for a short time.
Added sample data from Thai food dictionary

For the "Add missing information" and "Gather words" submenus, it will
make the most sense to work with some real(-ish) data, so I've added a
few entries from the Thai food dictionary as a good starting point. This
sample data isn't yet used, but pretty soon we'll have the lexService
functions returning the sample data, or specific subsets of it, so that
the forms we're designing can have some real data in them.

Once the database backend is written, of course, these services will be
updated to work with the real database.
Improve look of submenus