Creating first version of Readme file.

It should explain usage of the oneM2M base ontoolgy.

README.md

+The oneM2M Base Ontology 
+==============
+
+This is a private repository for developing the oneM2M base ontology
+
+The default branch will contain individual versions of the .owl files of the base ontology 
+(e.g. "base_ontology-v_3_5_0.owl"), matching the versions of TS-0012, which can be found at
+http://onem2m.org/technical/latest-drafts
+
+The repository will also contain a file "base_ontology.owl" which contains the latest version of the base ontology.
+
+For use in an ontology browser, e.g. Protege, one needs to use the link to the RAW version of the file, e.g. 
+https://git.onem2m.org/MAS/BaseOntology/raw/master/oneM2M_Base_Ontology-V_0_5_0.owl
+
+General
+-----
+ The classes and properties of the oneM2M base ontology are described in TS-0012.
+ 
+ Using this GitLab repository it is possible to create branches which contain your own ontology to be used in oneM2M.
+ Such an ontology needs to reference your own ontology as well as the base ontology - prefereably the latest version - via  "include" statements.
+ 
+ It also needs to contain appropriate subClass / subProperty relationship statements that make e.g. class yourDevice a sub-class of class Device of the base ontology.
+ 
+