Reorganise file structure for arduino-ino

The java-based arduino helper wouldn't compile on 64 bit but arduino-ino
seems to work. To get it to find all the files I had to move the
binclock stuff to lib/ and the other source files to src/. I've also add
.build/ to the .gitignore list; ino makes this directory to store files
while it builds and it shouldn't be tracked.
Add Time library for dealing with time
Declare every variable which uses PROGMEM as const

Without this ino won't compile the Time library at all.
Fix dependency in header file

It's been a while since I wrote C. Apparently I need to include the
binclock C source file in the binclock header file so that the functions
are callable when including the header file from other files. This also
means I can put my struct in the C file where it belongs and the code
compiles!