v0.7.1: rename C core header to victronble_core.h (fixes #2)

src/ held both VictronBLE.h and victronble.h. On case-insensitive
filesystems (Windows, macOS) extracting the library ZIP overwrote one
with the other and the Arduino build failed.

The core header is now victronble_core.h in include/ and src/, and every
include is updated. include/victronble.h stays as a deprecated forwarder
so 0.7.0 Zephyr and host code still builds; it is never in src/.

check_version.sh now fails if two tracked paths differ only in case.

library.properties

@@ -1,5 +1,5 @@
 name=VictronBLE
-version=0.7.0
+version=0.7.1
 author=Scott Penrose
 maintainer=Scott Penrose <scottp@dd.com.au>
 sentence=Portable library for reading Victron Energy device data via BLE on ESP32/S3/C3 and nRF52 (nRF52840/nRF52832)