[sr-dev] README-MODULES intro (please review)

[Olle E. Johansson]

SIP-ROUTER modules
==================

This is the first release of the combined project. In order to be able  
to support
an upgrade path for both Kamailio/OpenSER and SER current users, we  
have been forced to
provide some modules in two versions, which means that we have three  
set of modules:

  - modules:     the SIP router modules
  - modules_k:   Kamailio modules
  - modules_s:   SER modules

All modules are compatible with the core, so regardless if you are a  
new user or
an existing, you are free to make a choice between the three sets.
Note that if you are currently using one product, you want to select  
the module
that exists in the K/S directories first to get a smooth upgrade path.

As sip-router development progress, we will move as many modules as  
possible
into the core and only keep k/s modules for backwards compatibility  
when required.