Simple install guide and one-step install.sh

- README rewritten as a step-by-step guide for non-developers
- install.sh: build, install and copy data with plain error messages
- build_native.py: bundle identifier from the user's provisioning
  profile (Xcode project named factorio), version check on every
  build, friendly errors

install.sh

@@ -0,0 +1,42 @@
+#!/bin/sh
+# Builds Factorio for iPhone from your local Steam copy, installs it on the connected iPhone and
+# copies the game data. Safe to run again: data that is already on the phone is skipped and saves
+# are kept. Extra arguments are passed to tools/build_native.py (see docs/building.md).
+cd "$(dirname "$0")" || exit 1
+mkdir -p build
+LOG=build/install.log
+: > "$LOG"
+
+fail() {
+    echo
+    echo "Failed: $1"
+    echo "Details are in $LOG"
+    exit 1
+}
+
+step() {
+    # step "message" args... : run build_native.py with args, logging its output.
+    message=$1; shift
+    printf '%s... ' "$message"
+    if python3 tools/build_native.py "$@" >> "$LOG" 2>&1; then
+        echo "ok"
+    else
+        echo
+        if grep -q "not, or could not be, unlocked" "$LOG"; then
+            fail "device was not unlocked. Unlock the iPhone and run ./install.sh again."
+        fi
+        # build_native.py ends with a one-line explanation of what went wrong.
+        reason=$(grep -v '^+' "$LOG" | grep -v '^\s*$' | tail -n 3)
+        fail "$reason"
+    fi
+}
+
+command -v xcrun > /dev/null 2>&1 || fail "Xcode is not installed (README step 1)."
+xcrun --sdk iphoneos --show-sdk-path > /dev/null 2>&1 || fail "Xcode's iOS platform is missing (README step 1)."
+command -v python3 > /dev/null 2>&1 || fail "python3 not found; open Xcode once to finish installing its tools."
+
+step "Building the app" "$@"
+step "Installing on the iPhone" --no-build --install "$@"
+step "Copying game data to the iPhone (first time takes a few minutes)" --no-build --push-data "$@"
+echo
+echo "Done. Open Factorio from the iPhone home screen."