Allow the same text in multiple locations.

Resolves #1032.  Previously it was impossible to draw the same text,
with the same style, in two different locations, because the second
would end up using the first's cache entry, which only ended up moving
the element to a new position.

Now each cache entry holds a list of positions at which the text
appears, creating clones of the original element for each position
beyond the first.
Updated credits for various fixes in 0.8.1.
Updated version number to 0.8.1 final.
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Updated version number to 0.8.2-alpha.
Always set the axis innermost property.

It doesn't make sense to calculate the innermost property only when no
tickLength has been provided; the two have little to do with each other.
Fix incorrect check for the innermost axis.

An axis is innermost when it's first among those not just in its
direction, but also on its side, i.e. left/right, of the plot. So the
inArray check should be against the samePosition list, not all.
Resolves #1056.
Updated credits for the axis innermost fix.
Revert changes committed accidentally.

These changes were used to test the axis innermost property fix, and
should not have been committed.
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