Framework basics doc added

Framework basics.md

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+Hydra
+=====
+
+Haskell framework for building apps.
+- Web backends
+- Desktop apps
+- ...
+
+Properties:
+* Safe (more safe than bare IO)
+* Good testability
+* Separation of concerns, separation of business logic, interfaces and implementation
+  * Inversion of Control, Opacity, Interface segregation...
+  - interfaces: free monadic eDSLs: LangL, AppL, ...
+  - implementation: free monadic interpreters
+  - business logic: labyrinth, astro etc
+  - interfaces (free monad eDSLs) are abstracted (don't have any impl details)
+  - implementations (interpreters) know how to connect calls from business logic
+  to real calls and native libraries.
+* Layering
+
+------------------------------------
+
+Interfaces: hierarchical Free monadic languages
+
+* AppL
+  -
+  -
+  - evalLang (nests LangL scenarios)
+
+* LangL is an interface for some common actions
+
+  - getRandomInt
+  - evalIO
+  - throwException
+  - evalState (nests StateL methods)
+
+  - readVarIO   - read an STM-like variable
+  - writeVarIO  - write an STM-like variable
+  - newVarIO    - create an STM-like variable
+
+* StateL
+  - readVar
+  - writeVar
+  - newVar
+
+
+interpret readVarIO ----> readTVar   (real STM calls)
+interpret writeVarIO ----> writeTVar (real STM calls)
+interpret newVarIO ---->  newTVar    (real STM calls)
+
+
+STM (Software Transactional Memory)
+treads