Build: Convert docs directory to modern cmake

Add cmake files to docs directory. Remove unneeded cmake files.

By default, the targets are generated but not run by `make all` or
`make`. The documentation can be generated by running `make docs`

Please refer to the tfm_build_instructions document for
reference examples.

WARNING: This change will not build in isolation, it requires _all_
other cmake changes to successfully build. It is split out only for ease
of understanding.

Change-Id: I1b004a8f8ccfba2df901d91b093576fdc6bfa40d
Signed-off-by: Minos Galanakis <minos.galanakis@arm.com>
Signed-off-by: Raef Coles <raef.coles@arm.com>
diff --git a/docs/tfm_env.py.in b/docs/tfm_env.py.in
index b96be48..cc2f8bf 100644
--- a/docs/tfm_env.py.in
+++ b/docs/tfm_env.py.in
@@ -8,21 +8,18 @@
 # Interface file between cmake and sphynx-build. Variables will be populated
 # by cmake and evaluated by the Python builder
 
-cmake_env = { "SPHINX_TMP_DOC_DIR": "@SPHINX_TMP_DOC_DIR@",
-              "TFM_ROOT_DIR" : "@TFM_ROOT_DIR@",
-              "PLANTUML_JAR_PATH" : "@PLANTUML_JAR_PATH@",
-              "Java_JAVA_EXECUTABLE" : "@Java_JAVA_EXECUTABLE@",
-              "SPHINX_TMP_DOC_DIR" : "@SPHINX_TMP_DOC_DIR@",
-              "DOXYGEN_EXECUTABLE" : "@DOXYGEN_EXECUTABLE@",
-              "DOXYGEN_DOT_EXECUTABLE" : "@DOXYGEN_DOT_EXECUTABLE@",
-              "DOXYCFG_DOXYGEN_CFG_DIR": "@DOXYCFG_DOXYGEN_CFG_DIR@",
-              "DOXYCFG_OUTPUT_PATH": "@DOXYCFG_OUTPUT_PATH@",
-              "DOXYCFG_DOXYGEN_BUILD": "@DOXYCFG_DOXYGEN_BUILD@",
-              "DOXYCFG_ECLIPSE_DOCID": "@DOXYCFG_ECLIPSE_DOCID@",
-              "SPHINXCFG_TEMPLATE_FILE": "@SPHINXCFG_TEMPLATE_FILE@",
-              "PDF_OUTPUT_FILE": "@_PDF_FILE@",
-              "SPHINXCFG_COPY_FILES": "@SPHINXCFG_COPY_FILES@",
-              "SPHINXCFG_RENDER_CONF": "@SPHINXCFG_RENDER_CONF@",
-              "SPHINXCFG_TFM_VERSION" : "@SPHINXCFG_TFM_VERSION@",
-              "SPHINXCFG_TFM_VERSION_FULL" : "@SPHINXCFG_TFM_VERSION_FULL@"
+cmake_env = { "SPHINX_TMP_DOC_DIR"         : "@SPHINX_TMP_DOC_DIR@",
+              "TFM_ROOT_DIR"               : "@CMAKE_SOURCE_DIR@",
+              "PLANTUML_JAR_PATH"          : "@PLANTUML_JAR_PATH@",
+              "Java_JAVA_EXECUTABLE"       : "@Java_JAVA_EXECUTABLE@",
+              "DOXYGEN_EXECUTABLE"         : "@DOXYGEN_EXECUTABLE@",
+              "DOXYGEN_DOT_EXECUTABLE"     : "@DOXYGEN_DOT_EXECUTABLE@",
+              "DOXYCFG_DOXYGEN_CFG_DIR"    : "@DOXYCFG_DOXYGEN_CFG_DIR@",
+              "DOXYCFG_OUTPUT_PATH"        : "@DOXYCFG_OUTPUT_PATH@",
+              "DOXYCFG_DOXYGEN_BUILD"      : "@DOXYCFG_DOXYGEN_BUILD@",
+              "SPHINXCFG_TEMPLATE_FILE"    : "@SPHINXCFG_TEMPLATE_FILE@",
+              "SPHINXCFG_COPY_FILES"       : "@SPHINXCFG_COPY_FILES@",
+              "SPHINXCFG_RENDER_CONF"      : "@SPHINXCFG_RENDER_CONF@",
+              "SPHINXCFG_TFM_VERSION"      : "v@CMAKE_PROJECT_VERSION@",
+              "SPHINXCFG_TFM_VERSION_FULL" : "Version @CMAKE_PROJECT_VERSION@"
             }