Support for PC platform (#12)

* improvements for cross-platform compiling

* moved tactility-core to libs/

* splitup improvements

* remove git/gitmodules from freertos

* better platformbetter platform checks

* added build scripts

* delete mbedtls

* re-add mbedtls

* fixes and improvements

* added pc build

* simplify build scripts

* revert build scrpit

* updated builds

* fix for pc

* fix for pc

* fix for build

libs/mbedtls/tests/data_files/ecdsa_secp521r1.key

@@ -0,0 +1,7 @@
+-----BEGIN EC PRIVATE KEY-----
+MIHcAgEBBEIBsbatB7t55zINpZhg6ijgVShPYFjyed5mbgbUNdKve9oo2Z+ke33Q
+lj4WsAcweO6LijjZZqWC9G0Z/5XfOtloWq6gBwYFK4EEACOhgYkDgYYABAAd4ULV
+T2nrA47kt6+dPKB3Nv2c9xnrNU1ph57n88E2+w+/nwj4a+X6Eo7BoFHT5sZD6Fra
+j/rPNmPCYL0shEtvVgDO6OSKnmXQnK3YnyNd7gXzuKZGvnFfH2fVtDTg/yOh/Afv
+d0AZPkDu/287zf12WqkVUDNST+TyBfVETiksTC9qwQ==
+-----END EC PRIVATE KEY-----