ARM-8 W.I.P add tentative goals, var bindings, improve env handling

This commit includes:
* Tentative goals and non goals
* Start of motivation for some goals
* Improved way of handling environments and dynamic environments
* Binding of variables (required since they are delivered by an ENC)
* Typos, and other small adjustments

A second document examples.md is added with user stores (unfinished).
ARM-8 Replace comma with 'or' and allow 'and' as simple nesting.

It was hard to understand that when with comma separated list had
the meaning of "or". To make the language symmetrical, an "and"
is now also allowed with the same effect as a simple nesting.
ARM-8 Clarify that environments.pp file is evaluated on each request.
ARM-8 Add bindingsdir to environment defaults

Bindingsdir is the directory under which bindings are stored.
ARM-8 Add note about parameter unit mapping

Parameter mapping of the type {a => a, b => b} is a corner case
that could be supported with better concrete logic, but it is
expensive as it "destroys" bind map expressions. 

This commit adds a todo note about this consideration.
ARM-8 Add text about binding dependencies
ARM-8 Improve examples, fix typos, formatting errors
ARM-8 Fix typos in examples.
Merge pull request #56 from hlindberg/master

ARM-8 Add solution for dynamic environments, add example, add depedencies, variables....