Functional constraints

[jbcaillau]

@BaptisteCbl Following comments in previous PR:

• on the main version of constraint! (= the one with named args that factors out the code and is called by other / older versions without named args), we use lb/ub=Nothing if no bound (instead of +/-[ Inf, ... ])
• all other versions of constraint! (= without named args) do not have any default values and call the previous one (no code duplication)

When it is OK, can you please make a PR from your fork towards the constraint_revise branch?

PS. I suspect that the new version will also solve [#122]

[ocots]

If the other constraints! functions have no default values I suggest to change them as internal by writing __constraints!. Otherwise it may be confusing for the user.

I am not sure I haven't looked closely the code.

[jbcaillau]

@ocots For now, I advocate keeping them to ensure compatibility with previous functional syntax.

If the other constraints! functions have no default values I suggest to change them as internal by writing __constraints!. Otherwise it may be confusing for the user.

I am not sure I haven't looked closely the code.

[jbcaillau]

@BaptisteCbl Hi! Just merged this (long pending) PR: thanks for the job. Will have soon a closer look at the resulting changes in the related branch.

[ocots]

@jbcaillau have a look at #147