Rename to RTNode-HeltecV4, replace 'boundary' with 'transport' in docs

- Rename project from RNodeTHV4 to RTNode-HeltecV4
- Update GitHub repo URL, firmware binary names (rtnode_heltec_v4.bin, rtnode_heltec_v3.bin)
- Replace 'boundary node' with 'transport node' in README and flash.py descriptions
- Update OLED title bar to 'RTNode'
- Bump version to v1.0.18

.gitignore

@@ -3,7 +3,11 @@
 *.pyc
 TODO
 rnodethv4_firmware.bin
+rtnode_heltecv4_firmware.bin
+rtnode_heltec_v4.bin
 rnodethv3_firmware.bin
+rtnode_heltecv3_firmware.bin
+rtnode_heltec_v3.bin
 .firmware_cache/
 Release/*.hex
 Release/*.zip