api.rst and autosummary replaces long modules and classes doc pages (pvlib#258)

* add initial api doc

* add a bunch of functions and methods. almost all

* add autosummary and no_scrollbars to conf

* more modelchain and forecast stuff

* remove old classes and module files. fix typos

* remove cruft, add delta_t

* add note to whatsnew

Author: wholmgren

docs/sphinx/source/_static/no_scrollbars.css

@@ -0,0 +1,11 @@
+/* override table width restrictions */
+/* as described in https://github.com/snide/sphinx_rtd_theme/issues/117 */
+.wy-table-responsive table td, .wy-table-responsive table th {
+    /* !important prevents the common CSS stylesheets from
+       overriding this as on RTD they are loaded after this stylesheet */
+    white-space: normal !important;
+}
+
+.wy-table-responsive {
+    overflow: visible !important;
+}