Fix #402 - Add bikeshare support - Layers and Trip Plan (#776)

This is a 2017 Google Summer of Code project that implements bikeshare support, specifically:

1. Add a map Layers Floating Action Button, and a bikeshare map layer in the Nearby view
2. Adding bikeshare as an option in trip plans

Discussion surrounding bikeshare features is available in Issue #402.  See #776 for final screenshots of the 2017 GSoC project.

Other 2017 GSoC links for this project:
* [Initial proposal](https://github.com/OneBusAway/onebusaway-application-modules/wiki/Google-Summer-of-Code-2017)
* [Weekly Reports](https://groups.google.com/forum/#!topic/onebusaway-developers/uzN847x26UQ) to onebusaway-developers Google Group

CONTRIBUTORS.md

@@ -12,4 +12,5 @@ We'd like to thank the following developers who have contributed to OneBusAway A
 * Aziz Batihk
 * Charles Bond
 * Hillsborough Area Regional Transit (via Simon Jacobs at Cambridge Systematics)
-* Bridgette Eichelberger (bridgette@outlook.com)
+* Bridgette Eichelberger (bridgette@outlook.com)
+* Rodrigo Carvalho (carvalhorr@gmail.com)

icons/bike_markers/README.md

@@ -0,0 +1,34 @@
+# Bikeshare icons
+The images contained in this folder were used to generate the icons used for bike markers and speed 
+dial menu to select bike layer.
+
+## bike_marker_small.svg
+This image is displayed for all types of bikeshare (floating bikes and bike stations) when the map
+zoom is under level 13.
+
+It is converted into XML and loaded as BMP for use. To convert to XML use the Android Studio 
+Vector Asset generator.
+
+(instructions for Android Studio version 2.3.3)
+- Right-click folder res/drawable
+- Select New > Vector Asset
+- On the dialog that opens:
+    - Provide Path and Name and complete the action.
+
+ ## bike_floating_marker_big.svg
+This image is used for floating bikes when the map is on zoom level bigger than 13. It is used as PNG and was converted using the [Generic Icon 
+Generator](https://romannurik.github.io/AndroidAssetStudio/icons-generic.html).
+
+Parameters used:
+- Padding: 0%
+- Asset size: 32dp
+- Asset padding: 0
+- Color: (select transparent)
+
+## bike_station_marker_big.svg
+This image is used for bike stations when the map is on zoom level bigger than 13. It is also used 
+as PNG. Follow the instructions on the previous section to create the PNGs.
+
+## bike_speed_dial_selected.svg
+Image displayed on the layers speed dial menu when the bike layer is active. The counterpart to this 
+is the default material bike icon. Follow the instruction on the previous section to create the PNGs.