Remove old docs, rename docs_new to docs

It would be probably good idea to also remove tools/docgen.py and
asciidoc.mk, but asciidoc.mk is still mentioned under `cloud/doc`, which
may contain some useful info which we'll need at least to review before
removing.

PUBLISHED_FROM=faf454d4c52a2f07ea8ac084cf0bd11a0c9c9b3b

docs/c-api/net.h/mg_enable_javascript.md

@@ -0,0 +1,14 @@
+---
+title: "mg_enable_javascript()"
+decl_name: "mg_enable_javascript"
+symbol_kind: "func"
+signature: |
+  enum v7_err mg_enable_javascript(struct mg_mgr *m, struct v7 *v7,
+                                   const char *init_js_file_name);
+---
+
+Enable server-side JavaScript scripting.
+Requires `-DMG_ENABLE_JAVASCRIPT` compilation flag, and V7 engine sources.
+v7 instance must not be destroyed during manager's lifetime.
+Return V7 error. 
+