Rebrand hush3 to DragonX: binaries, defaults, and build system

- Rename binaries: hushd/hush-cli/hush-tx → dragonxd/dragonx-cli/dragonx-tx
- Default to DRAGONX chain params without -ac_* flags (randomx, blocktime=36, private=1)
- Update configure.ac: AC_INIT([DragonX],[1.0.0])
- Update client version string and user-agent to /DragonX:1.0.0/
- Add chainparams.cpp with DRAGONX network parameters
- Update build.sh, miner.cpp, pow.cpp for DragonX
- Add bootstrap-dragonx.sh utility script
- Update .gitignore for release directory

src/ac.json

@@ -13,7 +13,7 @@
       "ac_perc": "11111111",
       "ac_eras": "3",
       "ac_script": "76a9145eb10cf64f2bab1b457f1f25e658526155928fac88ac",
-      "clientname": "GoldenSandtrout",
+      "clientname": "DragonX",
       "addnode": [
         "node1.hush.is",
         "node2.hush.is",