Added Arduino example

Added an Arduino example.
A variation on 'Blink'

Arduino compatible folder heirarchy

Moved files and folders to allow the ETL to be put forward as a downloadable library.
Added a library.properties file.

Fixed cockup in ETL_ASSERT macro.

Fixed cockup in ETL_ASSERT macro where the condition test logic was reversed.

Minor changes to error macros

Changed error reporting macros to not evaluate to true or false. Macros are no longer able to be used in 'if' statements. ETL_LOG_ERRORS action changed/

Changes to the way errors are reported.

A new set of error macros allow more control of what type of error is produced and how it is reported.
Macros allow minimal code space and performance hits if required.

Major code improvements.

Many changes have been made to containers to reduce the code size by moving functionality to base classes.
New containers added.
New system for catching errors implemented.

Modified hash algorithms

The main change in this release is removing the generic interface to the hash algorithms.
The change was necessary to remove performance bottlenecks that could not be overcome with the classes derived from etl::ihash.

More STL style containers

Implementations of map, multimap, set, multiset, priority_queue.

Containers for non-default constructed elements

This release has all of the containers modified to allow elements with no default constructors.
Contains an incomplete implementation of etl::map.

Added etl::lookup

Added associative lookup container.