bugfix - rotate deselect no longer starts vector

a vector was being created on the click to deselect the rotate tool due
to the zoom click check.
clear button works

general Button class click detection appears to work
Delete button works
Component vector show button works
show bearing button working

Still not showing the values at the vector
bearing values showing at vector
components and bearings showing correctly on vectors
Merge pull request #5 from Cheddles/showVectorBearing

Show vector bearing
Mouseover button text implemented

not easily read when displayed over canvas. Consider fading out canvas
during button mouseover
change to vector numbering

selected vector is no longer moved to the end of the list. selectedCount
introduced to track the position of the selected vector
Revert "change to vector numbering"

This reverts commit 7484859cb25165074c7fb8003d97714f82a1dfdc.
change to vector numbering (corrected)

implemented int selectedCount to track the selected vector. On
selection, vectors are no longer reordered. Display still needs to be
reordered and dragging extended to all vectors.
Button dimensions generalised

mouseover text implemented
pushed button press code to global methods

shortens main draw() code and prepares to invoke the same code in
response to button presses later
next and previous buttons working
basic keypresses implemented
Invert button working but buggy

inverted vector is created but original is deleted.
Create inverse appears to work

may be buggy - need to fix dragging to check
dragging almost fixed

still drags at PI from correct bearing (at 1/3-2/3 magnitude from base)
y' component value displaying

With correct orientation for text. Still need to fix x' component value
to display on the outside of the triangle for arrows pointing down.