Add a prototype of vector like functions on 1D arrays

This commit adds the following methods to the _array record.  They currently
apply to 1D unstridable rectangular arrays only.  The methods that resize
the array assert at runtime that there is a 1:1 correspondence between the
array and its domain.

front() // return the first element of the array
back() // return the last element of the array
empty() // is the array empty?
push_back() // put a new value at the back of the array
pop_back() // remove a value from the back of the array
push_front() // put a new value at the front of the array
pop_front() // remove a value from the front of the array
insert() // insert a new value at a specified position and shift other elements

The methods that change the array size call reallocate every time instead of
doing something smarter like a doubling/halving scheme.

Added a test that does some pushes and pops on an array.
Added a test that tries to push_back an array declared over a domain has
multiple arrays.
Add a simple array vector operations benchmark

This shows the performance of array vector operations.  There is plenty of
room for improvement because every operation reallocates currently.  It
should work as a perf test.
Merge remote-tracking branch 'origin/master' into vectorArray
Change a config variable from param to const in test

Change a config param to config const so it can be set at runtime.
Adding some tests of the mkdir functionality for my own sanity.
Avoiding symbol collision.
Initial draft of associative primer
Removing associative content from domains primer
Informing reader to refer to associative primer
Making this example clearer
Merge branch 'master' of github.com:chapel-lang/chapel into assoc-primer
Adding associative primer to makefile
Add some new tests
Updating some of the other tests, as they weren't quite accurate
Initial implementation, passes the tests currently committed.
Merge remote-tracking branch 'origin/master' into vectorArray
Better header about other sources of information for domain types
Many style/wording/organization improvements. More examples of how associative arrays are 'just as good' as other arrays
Changing prettyPrint format to use brackets instead of curly braces. This is done to be more consistent with array-literal syntax
Add test to ensure mkdir with permissions works as expected.

Relies on process umask being set to 0022.  If this is not the case, this test
will break.